Kevin Warsh has been chair of the Federal Reserve for just four months, but this Wednesday will be remembered as the day he showed that he and his fellow governors, not outside forces, are the ones truly steering U.S. monetary policy. The Fed has done exactly what U.S. President Donald Trump did not want it to do under any circumstances: raise interest rates just six weeks before the midterm elections, in which Republicans risk losing control of Congress.

With this move, Warsh, a conservative billionaire appointed by Trump, has shown that he is serious about his commitment to fighting inflation, even if it means harming the electoral interests of the man who chose him in the belief that he would comply with his desire to make the United States the country with the lowest interest rates in the world. That has not been the case.

The increase is modest, at 25 basis points. The federal funds rate now stands in a range of 3.75% to 4%. But it is a powerful signal: it is the first rate hike in more than three years. The last came in July 2023. With this decision, Warsh’s Fed is underscoring its determination to bring inflation under control after more than five years in which prices have failed to move anywhere near the central bank’s 2% target.

The decision was also unanimous, ending a year marked by dissenting votes among members of the Board of Governors. That unanimity lends additional weight to the move and strengthens the Fed’s position against the criticism it is almost certain to face. One of the loudest critics is likely to be Trump. On Tuesday, he attacked the Supreme Court, particularly the three conservative justices he appointed during his first term, for ruling against his attempt to alter mail-in voting rules just weeks before the November 3 election. The three justices defied him, and now Jerome Powell’s successor, another Trump appointee, has done the same. Powell, too, eventually became a frequent target of Trump’s attacks.

Another significant takeaway is that Fed officials do not expect this to be the last increase. All but two members of the Board of Governors believe interest rates will need to rise again before the end of the year. Four policymakers anticipate two additional increases, according to the Fed’s latest projections. Warsh, who is reluctant to offer markets guidance about future decisions, does not participate in that forecasting exercise.

The Fed justified its move in a statement arguing that economic activity continues to expand at a solid pace despite heightened uncertainty, partly driven by geopolitical developments. “Job gains have kept pace with the workforce, and the unemployment rate has changed little. Inflation remains elevated. Today’s policy action will support a timelier return to the Committee’s 2% goal. The Committee will deliver price stability,” the statement said.

The rate hike came as no surprise to economists or to financial markets. Warsh had already signaled such a move at the Jackson Hole symposium in August. At the time, he said: “It’s the Fed’s job to make sure that inflation expectations do not get unanchored. […] We must be confident that underlying inflation is moving to our objective, clearly and at sufficient speed. Otherwise, we have work to do. That’s our job.”

A few days later, inflation data appeared to vindicate those arguing that the U.S. economy needed some cooling. Employment figures remain strong, but consumer prices in August held stubbornly at 3.4%, still a long way from the Fed’s 2% objective.

Trump’s threats

In recent days, Trump has escalated his attacks on the Fed, whose independence from the executive branch has been upheld by the Supreme Court. The president warned that unless interest rates were cut sharply, he would move to halt a significant portion of U.S. trade.

“LOWER THE RATE OR I’LL STOP TRADING WITH COUNTRIES WITH WHICH WE HAVE A DEFICIT, which the U.S. Supreme Court, in its ridiculous and very costly Tariff decision, strongly acknowledged ‘the President’ has an absolute right to do,” Trump said in a rambling post on his social media platform, Truth Social. Later that day, speaking from the Oval Office, he complained that other countries enjoyed lower borrowing costs than the United States and called on the Fed “to be patriots.”

Meanwhile, the war in Iran, which shows no signs of a near-term resolution, and the widening conflict involving Yemen’s Houthi rebels have kept oil prices above $100 a barrel, pushing up gasoline prices in the United States and threatening to fuel further inflationary pressures.

Before Friday’s decision, several analysts had warned that if Warsh wanted to preserve the Fed’s credibility as an institution capable of acting free from political interference, he had little choice but to raise rates. Doing otherwise might have pleased Trump and perhaps provided a modest boost to long-term growth prospects, but it would have pushed the goal of bringing inflation under control further out of reach and, above all, dealt a serious blow to the central bank’s independence.

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Neuroscientist Sergiu Pasca, 44, holds up a transparent vial filled with tiny white spheres floating in liquid. Each one is a cortical organoid, a millimetre-scale replica of the part of the brain responsible for complex thought, language and the mystery of the human mind. Pasca’s team implanted these seeds into the brains of mice that had been genetically altered so they would not develop a cerebral cortex of their own. The experiment, unique in the world, has produced healthy animals with brains that are an integrated blend of human and mouse. These animals contain more transplanted human neurons than any others ever born, the scientist tells EL PAÍS.

For the first time, these animals make it possible to investigate “features of the human brain that until now were inaccessible,” says Pasca, a physician and researcher at Stanford University in the United States. Specifically, they allow scientists to study the human neurons most characteristic of our species at the molecular and cellular level within a living organism, rather than in a cadaver sample or a laboratory cell culture, as has been the case until now. Pasca, who was born in Romania, believes the advance paves the way for new treatments for autism, schizophrenia, cerebral palsy and dementia. In the future, he says, it may be possible to create a mouse with a cerebral cortex made from an individual patient’s own neurons.

The details of the experiment, published on Wednesday in Nature, read like science fiction. It begins with skin cells taken from healthy volunteers. Scientists apply a cocktail of proteins that reprograms the cells back to an embryonic state, when they can become any tissue in the body. The cells are then guided to develop into the type of stem cells that give rise to neurons in the cerebral cortex, eventually forming organoids: the tiny white spheres with a three-dimensional structure that Pasca displays during the video interview.

In earlier experiments, the same team successfully implanted human neurons into the brains of rats and used laser light to influence their behavior. Growth, however, was limited by the lack of space inside the skull, as human neurons are much larger than those of rodents. Pasca had also shown that organoids from different regions of the brain can be created and fused together, like pieces of a living puzzle.

These spheres, each containing hundreds of thousands of human neurons, are implanted into the mice two days after birth. They then begin to grow, become vascularized and connect with the rest of the mouse brain, which controls functions such as sensory processing and movement. Because the animals lack their own cerebral cortex, the human neurons expand to make up more than 90% of the cortex and roughly half of the mice’s entire brain. Timing is crucial: this window of “plasticity,” during which the cells can integrate with their host, closes about two weeks after implantation.

The cerebral cortex that develops in these mice is comparable to that of a human fetus in the sixth month of gestation, Pasca explains, although there are important differences. At that stage, the human brain already contains more than 16 billion neurons, whereas the modified mice have around four million such cells in their cortex. A normal mouse brain, by contrast, contains about 14 million neurons, because its neurons are much smaller. What exists inside the brains of these engineered animals is not exactly a human cerebral cortex, as some cell types are still missing and neither the structure nor the size is fully equivalent. Even so, Pasca argues that it provides an invaluable model for studying our “most inaccessible organ.”

Cerebral palsy

In a proof-of-concept experiment, the researchers cut off the oxygen supply to the brains of their humanized mice. Ordinary mice are remarkably resistant to this kind of injury, whereas in humans even a brief period of oxygen deprivation can result in lifelong cerebral palsy.

The lesions observed in the animals with humanized brains resemble those seen in patients with cerebral palsy, a condition that affects around 18 million people worldwide. The team argues that these mice make it possible, for the first time, to study the effects of these currently irreversible injuries in a living brain, and perhaps even to identify ways of treating them.

In 2024, Pasca’s team implanted human brain organoids derived from the cells of a child with Timothy syndrome — a rare genetic disorder associated with severe autism and epileptic seizures — into rats. The work enabled the researchers to develop a genetic therapy that reversed the condition in the implanted animals. Pasca says the team plans to begin testing the treatment in humans in a clinical trial later this year or early next year.

Garikoitz Lerma-Usabiaga, an Ikerbasque researcher at the Basque Center on Cognition, Brain and Language (BCBL) in San Sebastián, contributed to the study by characterizing the brain’s microstructure using diffusion MRI. This technique measures the movement of water molecules to determine tissue organization and map neuronal pathways. “The technique finds that water molecules prefer to travel in the direction from the human organoid to the mouse brain, suggesting connectivity between the two,” the neuroscientist explains.

The researchers were in for another surprise. These mice generated a type of neuron that had never before been isolated in a living organism: Von Economo neurons, a rare class of neural cell first described in 1925. Initially thought to exist only in humans, they were later identified in primates and in other mammals with large, complex brains, including elephants, whales and dolphins.

These neurons are found in regions of the cortex associated with social behavior and decision-making, and their premature degeneration is a hallmark of frontotemporal dementia, a rare form of the disease that appears between the ages of 40 and 60.

The researchers believe these unusually large neurons may have emerged in the humanized mouse brains because, for the first time, they had sufficient space to develop. Their presence could now provide a valuable platform for testing treatments for the disease.

Despite having a cortex made up of human neurons, these animals do not behave very differently from ordinary mice, Pasca says. If anything, they are slightly slower in tests of memory and reflexes, because the connection between the human and mouse components of the brain “is not perfect.” That is due to the fact that the two species have been evolving separately for more than 70 million years.

Ethical issues

The outcome would likely be very different if these human organoids were implanted into monkeys, something that should not be done for ethical reasons, according to Pasca. Before carrying out the mouse experiments, his team submitted the project to an independent oversight panel made up of bioethicists, lawyers, evolutionary biologists, patient advocates and philosophers, all of whom approved the work.

“It is a very delicate subject, and it is easy for misunderstandings to arise if we do not convey the nuances well,” says Pasca, who argues against replicating this experiment in apes: “In species closer to us, human neurons would have much more space to grow, and integration would be much better. I think we should be very cautious about this kind of experiment and not carry them out unless there is a very clear justification.”

Daniel Tornero, head of the Stem Cell and Brain Injury Laboratory at the University of Barcelona, is well acquainted with Pasca’s work and describes it as “incredible.” “Psychiatric illnesses are the hardest to model because mice do not suffer them, and their cerebral cortex is much smaller,” he explains. “This new work is interesting because it allows you to model human diseases with human cells.”

In 2019, a Chinese team that included the Spanish biologist Juan Carlos Izpisua created the first human-monkey chimera: a macaque implanted with stem cells derived from humans. The aim was to explore whether animals could one day be used to grow human organs for transplantation. The term chimera comes from the fire-breathing creature of Greek mythology, with a lion’s head, a goat’s body and a dragon’s tail.

For Tornero, the animals created by Pasca are also chimeras, although the Stanford researcher is careful to avoid the term, perhaps to steer clear of controversy. Tornero notes that it is difficult to know whether there is anything human in the behavior or thought of these mice.

“Human neurons send axons [projections] into the mouse brain, but there is not enough data yet to know whether those connections are superior,” he says.

The possibility is not purely theoretical. In 2013, a research team demonstrated, on a much smaller scale, that injecting 300,000 human glial cells, which provide support and immune protection in the brain, into mice could enhance their cognitive abilities. The modified rodents had better memory and learned faster than normal ones.

For now, however, these new animal models can only be used to study disorders that arise during embryonic development. Human neurons grow about 20 times more slowly than those of mice. Even if one of these animals lived to the age of two, the upper limit of a mouse’s lifespan and roughly equivalent to old age in humans, its cerebral cortex would still resemble that of a two-year-old child.

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Claire-Louise Bennett has said she is fascinated by the ways we exist in other people’s minds, by what we become when we are reduced to an idea. Perhaps that is why her fiction is always filtered through a consciousness: someone obsessively searching for a way out, or for a place in the world. Is love a kind of compass? Can it give shape to the self, each time in a different way?

Bennett thinks it should, but she also believes we are increasingly preventing it from doing so. Dating apps are no help, she says. In her latest novel, the intense, labyrinthine and deeply interior Big Kiss, Bye-Bye, she asks how love places us before a mirror and reveals the parts of ourselves we would never admit are also there. And something like that can only be reached, as Anaïs Nin might have put it, through the mystery of what draws us to another person when nothing has been agreed in advance.

At her home in Galway, Ireland, Bennett, who is also the author of Checkout 19 and Pond, answers the video call. She is seated at an enormous table. It is covered with notebooks and crystal spheres. Nearby, she says, there is even a glass penguin. And the mug from which she occasionally takes a sip still contains some of the Yogi Choco tea she made for herself a little while ago.

Question. Big Kiss, Bye-Bye is a long conversation between two lovers that recalls both the obsessive prose of Thomas Bernhard and the stream of consciousness of Virginia Woolf. In that conversation, Xavier functions as a kind of totem, a looming presence against which the narrator defines herself, sketching an outline of who she is and making herself real. To what extent is love a kind of existential compass?

Answer. I love the image. Yes. Without a doubt, it is. I deeply believe that love is an existential experience. I read Alain Badiou’s In Praise of Love a long time ago and felt he was right about everything. At the center of the experience of love should be difference, chance and risk — elements that today, in a world dominated by app-mediated dating, are practically impossible. Today’s world encourages us to think in terms of compatibility. We look for someone who fits us, who reaffirms who we already are. That very conscious way of approaching relationships can be quite transactional, like shopping, because it forces us to define in advance what we are looking for in a partner, what we expect from a relationship and what our limits are. Love is the opposite. Love is the great revealer.

Q. In what sense?

A. Love reveals who we really are. It shows us things about ourselves we would never have dared to imagine, much less admit. That is why attraction that arises in real life has such enormous force and, at the same time, is so unsettling. Anaïs Nin was terrified of being fixed into a stable, defined personality. She wanted to flow, to be always transforming, and for her love, made that perpetual motion possible — that existential expansion. Her stories and novels show how intimate encounters can uproot you, turn your world upside down, take you far from whoever you think you are at that moment. What today might be dismissed as mere romanticism is, in reality, what makes love a deeply singular experience. After all, it is the most powerful force there is, provided one has the courage not to try to manage or direct it.

Q. In your case, writing itself also seems to function as a compass, a way of finding your path through words and through what words construct: fragmentary scenes, memories seen from a single perspective, disorientation, something mutable and therefore open to transformation. Would you say that’s true? What are we, really? Everything we might yet become, or everything we have been?

A. Sometimes I feel I do not have a self, at least not in a strict sense. What I am is a place where very diverse forces orbit — and sometimes conflict —: archetypes, psychic patterns, impulses and memories both personal and collective, and many other things. There is a huge part of what I am that is completely unknown to me. And yet I know those unknown elements exert a huge influence on my everyday life. It is tempting to use writing as a way to make sense of that chaos and learn to navigate it, but the satisfaction it offers is only superficial. That is not what I am looking for. Samuel Beckett said the artist’s task is not to clarify things, but to find a way to make room for disorder. I completely agree.

Q. Is that why your writing has this quality of being unreliable, of constantly transforming itself?

A. Yes. My writing follows a winding path, full of false starts, dead ends, and overgrown landscapes. And, every now and then, small clearings appear where there is a sense of respite, immediacy, and communion. The thing is, I don’t write to affirm anything. I write by denying, subverting, and undermining. And that’s because, although we need to place some faith in reality in order to keep on living, deep down I don’t believe that what we call reality actually exists.

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